Many methods have been employed to analyze data from experiments which measure transient responses to excitations. One such experiment,deep level transient spectroscopy, is widely used in the study of semiconductor defects. The covariance method of linear predictive modeling, which is used in digital signal processing, can be applied to the problem of transient analysis. We describe the covariance method and its limitations, and present the results of its use to analyze the data from capacitance transient experiments.

The possibility of using the phase shift of the acoustic signal of different constituents as a new tool for a depth profile analysis of layered samples is discussed. This new method is experimentally demonstrated by measuring the phase variations of the photoacoustic detected ferromagnetic resonance of a sample consisting of an ironfilm bonded to a nickelfilm.

The composition dependence of the as‐deposited structure, the insitucrystallization sequences, and thermal stability were investigated for evaporated Gd‐Fe alloyfilms. The composition dependence of the structural variations in the as‐deposited alloyfilms, the glass forming range, and the crystal size variation in the microcrystalline regions are consistent with the predictions of a model using hard spheres of two different sizes. The insitucrystallizationreaction of Gd‐Fe alloyfilms was characterized by the three reaction stages. (1) α‐Fe and α‐Gd were precipitated by the primary crystallization. The growth of primary crystals is characterized by a continuous process. (2) Some intermetallic compounds were formed by a polymorphous reaction. The growth of these phases is characterized by a discontinuous process. (3) The equilibrium phases are formed by decomposition reaction which was not detected in this study. The Gd atom array in the amorphousstructure is concluded to be similar to the Fe atoms array of tetrahedra connected at corners. The thermal stability of the amorphousstructure is the highest and growth rate of the primary crystals is the lowest at around 33 at. % Gd which is the composition of the close packed cubic Laves phase.

The activation energies of thermal donors and of the A center in silicon, the oxygen vacancy complex, are measured as a function of hydrostatic pressure by Hall effect and by deep level transient spectroscopy. The A center is classified as a deep level because the strong pressure dependence of its activation energy indicates a short‐range potential. In contrast, thermal donors are true shallow levels associated with a long‐range coulomb potential because of the low pressure dependence of their activation energy. Based on these results, an atomic model for thermal donors is suggested, consistent with results of investigations concerning pressure dependence of energy levels, formation kinetics, IR absorption, electrical activity, and electron paramagnetic resonance.

The behavior of misfit dislocations in (111)A InP/In0.53Ga0.47As/InP double heterostructure (DH) wafers, grown by liquid phase epitaxy, has been investigated by x‐ray and photoluminescence(PL)topography and compared with those in (100) and (111) B quaternary DH wafers. Misfit dislocations are generated at wafer edges and are located in close proximity to the heterointerface in the upper InP layers. These dislocations were determined to be the same as in the case of (100) DH wafers. The misfit dislocation free area, as determined by PLtopography with Ar+ion laser excitation, decreases rapidly when the upper InP layer thickness approaches about 1 μm. Nearly misfit dislocation free DH wafers were obtained by a two step growth of the upper InP layer. In (111)A ternary DH wafers, with a lattice mismatch of 0% to −0.03% at room temperature, misfit dislocations are mostly β‐type 60° dislocations. These misfit dislocations are not observed by PLtopography when ternary layers are excited by a Nd‐doped Yttrium Aluminium Garnet (Nd:YAG) laser. Misfit dislocations of the α type, introduced in (111)B quaternary DH wafers with a lattice mismatch of the same sign and magnitude, are clearly observed as dark lines under Nd:YAG laser excitation.

Three implantation effects were investigated in floating‐zone‐grown silicon: (a) the effect of Cl+ implantation resulting in the shrinkage of oxidation‐induced stacking faults; (b) the effect of F+ implantation giving rise to defaulting of the 1/3[111] Frank dislocations into 1/2[110] perfect dislocations due to the interaction with 1/6[112̄] Shockley partials; (c) the effect of a combined F+ and Cl+ implantation of dislocation motion. Notwithstanding the limited magnification of double‐crystal x‐ray topography it proves to be a valuable technique for determination of the effects of implantation, as removal of F; the oxidation layer is unnecessary for observation of the oxidation‐induced stacking faults. Moreover, the role of the oxide layer in the Si‐SiO2 interface can be followed more appropriately.

Depth distributions for sulfur (S) implanted in (100) and (111) silicon (Si) measured by secondary ion mass spectrometry are reported for S ion energies from 40 to 600 keV and ion fluences from 4×1012 to 4×1016 cm−2. The results of Pearson IV fits are tabulated for the energy and fluence series; the range parameters given are peak depth (Rm) and μ(Rp), σ(ΔRp), γ1, β2, and β′2 for both the peak of the distribution and the full curve (including the influence of the channeling tail). The S densities are measured from a maximum of 1021 down to <1015 cm−3 where the detection limit is probably caused by background oxygen (mass 32). Sulfur profiles are shown for annealing temperatures from 100 to 950 °C in (100) and (111) Si orientations. Sulfur is retained in the region of damage for densities above about 1018 cm−3, until an annealing temperature of 900 or 950 °C is reached, when the S is largely rejected from the Si crystal; the remaining S density is <1015 cm−3, in agreement with solidsolubility.

We report electron spin resonance(ESR)measurements of E′‐center (a ‘‘trivalent silicon’’ center in SiO2) density as well as capacitance versus voltage (C‐V) measurements on γ‐irradiated metal/oxide/silicon (MOS) structures. We also report a considerable refinement of earlier ESRmeasurements of the dependence of radiation‐induced Pb ‐center (a ‘‘trivalent silicon’’ center at the Si/SiO2 interface) occupation as a function of the Fermi level at the Si/SiO2 interface. These measurements indicate that the Pb centers are neutral when the Fermi level is at mid‐gap. Since the Pb centers are largely responsible for the radiation‐induced interface states, one may take ΔVmgCox/e (where ΔVmg is the ‘‘mid‐gap’’ C‐V shift, Cox is the oxide capacitance, and e is the electronic charge) as the density of holes trapped in the oxide. We find that radiation‐induced E′ density equals ΔVmgCox/e in oxides grown in both stream and dry oxygen. Etch‐back experiments demonstrate that the E′ centers are concentrated very near the Si/SiO2 interface (as are the trapped holes). Furthermore, we have subjected irradiated oxide structures to a sequence of isochronal anneals and find that the E′ density and ΔVmgannealing characteristics are virtually identical. We conclude that the E′ centers are largely responsible for the deep hole traps in thermal SiO2 on silicon. This observation coupled with observations regarding the Pb center indicates that two intrinsic centers, both involving silicon atoms lacking one bond to an oxygen atom, are largely responsible for the two electrically significant aspects of radiation damage in MOS devices: charge buildup in the oxide and interface‐state creation at the Si/SiO2 interface.

The formation of CrSi2 by ion mixing was studied as a function of temperature, silicide thickness and irradiated interface. Samples were prepared by annealing evaporated couples of Cr on Si and Si on Cr at 450 °C for short times to form Si/CrSi2/Cr sandwiches. Xenon beams with energies up to 300 keV and fluences up to 8×1015 cm−2 were used for mixing at temperatures between 20 and 300 °C. Penetrating only the Cr/CrSi2 interface at temperatures above 150 °C induces further growth of the silicide as a uniform stoichiometric layer. The growth rate does not depend on the thickness of the initially formed silicide at least up to a thickness of 150 nm. The amount of growth depends linearly on the density of energy deposited at the interface. The growth is temperature dependent with an apparent activation energy of 0.2 eV. Irradiating only through the Si/CrSi2 interface does not induce silicide growth. We conclude that the formation of CrSi2 by ion beam mixing is an interface‐limited process and that the limiting reaction occurs at the Cr/CrSi2 interface.

A linear array of screw dislocations in front of a mode 3 crack lying on a plane inclined to the crack is studied. The problem is formulated in terms of an integral equation describing the equilibrium condition between the dislocations and the crack under an externally applied shear stress. The distribution function for dislocations is derived from a solution of the integral equation by applying the Wiener–Hopf technique. The condition of finite stress at the end of the pileup, or the Bilby, Cottrell, and Swindeman (BCS) condition and the crack opening displacement (COD) are obtained in simple analytical forms as a function of the angle of inclination. Numerical results show that, for a given applied stress, the distribution function, the length of the plastic zone, and the COD decrease only slightly as the angle of inclination increases from 0 to π/2. The quantity of σf COD , where σf is the friction stress, is shown to be equal to the radial component of the complex J integral and, hence, is the total force on the dislocations along the direction of the pileup. A method to estimate results under mode 1 condition involving an inclined pileup of edge dislocations is considered.

Aluminum contacts to shallow junctions in high‐performance siliconintegrated circuits suffer from an inhomogeneous Al/Si interaction, which culminates in a destruction of contact and junction integrity. Certain silicides such as CoSi2, on the other hand, are thermodynamically stable over Si. However, these still require an additional barrier layer between the top Al and the silicide to inhibit thermally induced reactions with Al. This work addresses the question of electromigration at one such proposed contact metallization scheme consisting of Al/TiN/CoSi2. Results indicate that the TiN provides a suitable barrier to Al/Si interdiffusion under standard device operating conditions. At extremely high currents and temperature, however, the contacts degrade by a localized Al/TiN interaction, which destroy the TiN barrier integrity, followed by Al/CoSi2 reaction and Si electromigration from the substrate. In contrast, Al/CoSi2 contacts are highly susceptible to junction leakage, with junction lifetimes controlled by the kinetics of Si diffusion through CoSi2.

A numerical solution of the problem of diffusion via a dual mechanism is obtained for P, As, and B diffusion in Si by solving the full system of impurity, vacancy, and self‐interstitial continuity equations. The suitable constants are derived by fitting on experimental results for diffusions in both inert and oxidizing ambients, and lead to interesting information on siliconpoint defects at high temperature. In particular, it is found that dopantdiffusion is essentially vacancy assisted, whereas self‐diffusion proceeds primarily via self‐interstitials.

The diffusivity of Ti into LiNbO3 has been measured as a function of crystal orientation and Li/Nb ratio in the temperature range 980–1112 °C. The Li/Nb ratios of single crystal samples were adjusted by vapor phase equilibration with fixed Li2O activities. No anisotropy of diffusivity with crystal orientation could be detected. The diffusion constants for Ti in LiNbO3 decrease with increasing Li2O content. At 1050 °C, the values decrease from 2.60×10−12 cm2/s at the Li2O‐deficient phase boundary (48.1 mol % Li2O) to 1.06×10−12 cm2/s at the congruently melting composition at (48.6 mol % Li2O) to 0.4×10−12 cm2/s at the Li2O‐rich phase boundary (50.0 mol % Li2O). It is suggested that enhanced lateral diffusion observed for stripe geometry Ti sources results from increased diffusivity in a surface layer formed by Li2O outdiffusion.

Growth kinetics of rhodium silicide in the temperature range of 375–450 °C have been studied on three different silicon substrates: single crystal,polycrystalline, and amorphous. The methods of analysis and specimen characterization utilized in this study are Rutherford backscattering spectroscopy (RBS), Seemann–Bohlin x‐ray diffraction, cross‐sectional transmission electron microscopy(TEM), sheet resistivity via four‐point probe, and Schottky barrier height measurements obtained from the current‐voltage relationship. Our results conclude that all three silicon substrates form an identical rhodium silicide compound, RhSi, indicating that the crystallinity of the substrate has no effect on the resulting rhodium silicide. The growth of RhSi was determined to be diffusion‐limited and the activation energy of growth was similar for single crystal (1.88±0.04 eV) and amorphous silicon (1.86±0.07 eV), yet it was slightly lower (1.71±0.08 eV) for polycrystallinesilicon. The difference can be attributed to the rhodium silicide compound having a smaller grain size in the polycrystallinesilicon case. The layer formation and the thickness of rhodium silicide between unreacted rhodium and the three different siliconstructures was examined by cross‐sectional TEM and compared to those measured by RBS.

We have investigated the deposition conditions necessary to produce optimized films of A15 Nb‐Sn (19–26 at. % Sn) by electron‐beam codeposition. Reliable high‐quality superconducting tunnel junctions can be made on this material by using an oxidized‐amorphous silicon overlayer as the tunneling barrier and lead as the counter‐electrode. These junctions have been used both as a tool for materials diagnosis and as a probe of the superconductingproperties (critical temperature and gap) of the films. Careful control of the substrate temperature during the growth of the films has proved critical to obtain homogeneous samples. When the substrate temperature is properly stabilized, stoichiometric Nb3Sn is found to be relatively insensitive to the deposition temperature and conditions. In contrast, the properties of the off‐stoichiometry (Sn‐poor) material depend strongly on the deposition temperature. For this Sn‐poor material the ratio 2Δ/kTc at a given composition increases with increasing deposition temperature. This change appears to be due to an increase in the gap at the surface of the material (as measured by tunneling) relative to the critical temperature of the bulk. All the tunnel junctions exhibit some persistent nonidealities in their current‐voltage characteristics that are qualitatively insensitive to composition or deposition conditions. In particular, the junctions show excess conduction below the sum of the energy gaps (with onset at the counter‐electrode gap) and a broadened current rise at the sum gap. The detailed origins of these problems are not yet understood.

The interrelation between dimeric and tetrameric arsenic sources and high‐ (700 °C) and low‐ (600 °C) growth temperatures on the properties of GaAs/(Al,Ga)As superlattices has been investigated. Superlattices consisting of alternating 100‐Å‐thick layers of GaAs and (Al,Ga)As were grown by molecular beam epitaxy and characterized by low temperature photoluminescence and excitation spectra. At low growth temperatures, the quality of the superlattice can be improved substantially by using As2 instead of As4. At 700 °C the arsenic species do not have as much an effect on the overall quality, but varying the group V/III ratio changes the relative intensities of the observed multiple excitonic peaks. These peaks are separated from one another by less than 1 meV, indicating extremely sharp and high quality interfaces and making it possible for the first time to relate them to excitonic processes.

The oxygen behavior and its influence on Ti silicide formation is systematically studied in the TiO2/Si and Ti/TiO2/Si systems using Rutherford backscattering,nuclear reaction analysis, and x‐rays diffraction techniques. After annealing in vacuum ( p<5×10−7 Torr), no reaction was observed up to 900 °C in the TiO2/Si system, whereas in the Ti/TiO2/Si system, metallic titanium reacts with the TiO2film above 400 °C and at 600 °C a uniform oxygen solid solution is formed. The silicide formation starts at 650 °C and up to 750 °C the only phase formed is Ti5Si3. We found that this phase is kinetically favored as long as the Ti is being supplied by the unreacted film. The growth rate kinetics was found to have parabolic behavior and was therefore controlled by Si volume diffusion. Above 750 °C, TiSi2 forms very rapidly, its growth being nucleation controlled. During the growth of the silicide layer, a diffusion of oxgen toward the surface region was observed. When the oxygen concentration in the surface layer exceeded the solubility limit, Ti oxide precipitated and the silicide growth nearly stopped, even if some silicon reached the surface. At a temperature higher than 850 °C, a marked oxygen loss takes place, most probably via SiO sublimation. The sublimation process is favored by the presence of Si in the surface region and prevents the formation of a stable SiO2 diffusion barrier at the TiSi2/TiOx interface.

Heteroepitaxialgrowth of vacuum‐evaporated Si films on CaF2/Si structures has been investigated. In order to prevent surface reaction between deposited Si and the underlying CaF2films at high temperatures, a thin Si layer is insitudeposited at room temperature onto the CaF2surface prior to deposition of Si at 800 °C. It has been shown from morphological and ion channeling studies that the thin predeposited Si layer, less than 10 nm in thickness, is useful to prevent the surface reaction without destroying the epitaxialgrowth, and that this technique is applicable to both (111) and (100) oriented substrates. The early stage of the growth is also studied. It has been found that the majority of the predeposited Si layer is not aligned to the substrate orientation even after a thick film has grown epitaxially. A possible model for the epitaxialgrowth is discussed.

The use of P2 and As2beams generated by several different beamsources for the growth of InP,GaAs, and GaxIn1−xPyAs1−y has been investigated. Accommodation coefficients for As2 and P2 were determined for heated GaAs and InP surfaces. It is demonstrated that a source utilizing decomposition of the hydrides over the range 200–2000 Torr and providing a leak of the resulting P2, As2, and H2 molecules into a molecular beam epitaxy(MBE) system can be used for the growth of GaxIn1−xPyAs1−y layers lattice matched to InP.Heterostructure lasers emitting at 1.5 μm with room temperature threshold current densities of 2000 A/cm2 and differential quantum efficiencies of 17%–19% were fabricated to demonstrate the quality of the epitaxy by this method. Initial studies of the cracking of AsH3 and PH3 at low pressures in contact with heated Ta suggest that Ta acts as a catalyst for the decomposition and that low pressure beamsources may also be useful for gas sourceMBE.

The density of localized states in the mobility gap of evaporated amorphous siliconfilms has been measured over a range of 250 meV between the conduction band and the Fermi level. The method employed is based on the analysis of the phase shift between an intensity modulated exciting light and the associated photocurrent induced in the semiconductor. The density of states falls off almost exponentially with energy away from the conduction band. It suggests an overlap of the conduction and valence band tails, a result consistent with the Cohen, Fritzsche, and Ovshinsky model.